The present invention relates to a production tamper machine for selectively tamping ballast simultaneously underneath two successive ties or underneath a single tie of a track including a plurality of spaced ties resting on the ballast and defining cribs between adjacent ones of the spaced ties, and rails having a gage side and a field side, the rails being fastened to the ties. The machine comprises a respective tamping head associated with each rail and operative for production tamping. Each tamping head comprises a common tamping tool carrier, two pairs of opposed vibratory tamping tools mounted on the common tamping tool carrier laterally adjacent each side of the associated rail, the tamping tools of the pairs of tools on one rail side being transversely aligned with the tamping tools of the pairs of tools on the other rail side, the tamping tools including tamping pick means with tamping jaw means wide enough for effective production tamping, the pairs of tools being spaced from each other in the direction of elongation of the track, with one of the opposed tools of one of the pairs being adjacent one of the opposed tools of the other pair while the other tools of the pairs of opposed tools are remote from each other. The spacing between the pairs of tools is such that the adjacent tools of the two pairs may be immersed in a respective one of the cribs defined between the adjacent ties, the opposed tools of each pair being arranged for immersion in the ballast adjacent one of the ties, with the one tie positioned between the opposed tools, and for reciprocation in the direction of elongation of the track. Reciprocating drives are connected to the opposed tamping tools, as well as a common drive for vibrating the tamping tools. A drive is provided for vertically adjusting the tamping tool carrier. This invention also relates to the tamping head for such a production tamper machine.
Tamping heads of this type for tamping two successive track ties simultaneously have been disclosed in U.S. Pat. Nos. 3,357,366 and 3,372,651. In U.S. Pat. No. 3,357,366, twin tamping tools are used on each side of the rails. Producticn tampers incorporating such tamping heads have been used commercially with great success because their operation not only considerably increases the tamping efficiency but also enhances the uniformity of the ballast compaction underneath the ties because two adjacent tamping tools are immersed in the same crib and are simultaneously reciprocated in opposite directions. However, when such machines are used for tamping track having quite irregular crib widths and/or obliquely disposed ties and/or at double ties disposed under rail joints, difficulties have been encountered because it is then not always possible readily and rapidly to center the tamping tools properly so as to assure proper tie tamping and to avoid possible damage to the ties.
As is common in this art, the term "production tamper" or "production tamping" used throughout the specification and claims refers to tamping ballast along stretches of tangent or curved track in regular track rehabilitation work, in contrast to such specialty tampers as "switch tampers" designed for work in track switches. Production tamping can be effected only with tamping tools which include tamping pick means with tamping jaw means wide enough for effective ballast tamping, i.e. equivalent to twin tamping picks at each side of the rails. While production tampers have been designed for working also in track switches, certain specialty tampers can work only under the special tamping conditions for which they are designed.
U.S. Pat. No. 3,534,687 deals with a switch tamper designed to tamp two adjacent ties simultaneously. The tamping head of this machine provides only a single tamping tool at each side of the rails and these tamping tools may be pivoted upwards in a plane extending perpendicularly to the plane of reciprocation of the tamping tools. A hydraulic cylinder-piston adjustment drive is linked to each tamping tool for pivoting the same. The tamping head is mounted with a track correction reference system on a machine frame portion which is cantilevered over the track section to be corrected and tamped, and which is laterally pivotal on a main machine frame portion to enable the tamping tools to be properly centered in track switches. Adequate production tamping is impossible with this machine and, in addition, the machine requires 16 separate adjustment drives with associated bearings and controls, wherefore this machine has proved not to be commercially feasible.
U.S. Pat. No. 4,282,815 discloses a production tamper machine designed for simultaneously tamping two successive ties. For this purpose, closely adjacent single-tie tamping tool assemblies are vertically adjustably mounted on a common frame and separate drives are used for the vertical adjustment of each tamping tool assembly. Each tamping tool assembly comprises two pairs of opposed vibratory twin tamping tools arranged for reciprocation in the direction of track elongation, the pairs of tools being laterally adjacent the gage and field sides of the rails, and the opposed tools of each pair being arranged for immersion in the ballast adjacent a respective tie, with the tie positioned between the opposed tools. This structure requires not only two vertical adjustment drives but also eight vibrating drives, i.e. two vibrating drives for each pair of tamping tools, which makes it quite expensive to build and service. It has the added disadvantage that the adjacent tamping tools of the pairs cannot be disposed sufficiently close to each other--due to the special types of reciprocating and vibrating drives used--to enable the machine to assure trouble-free reciprocation of the tamping tools and operation as a tamper for two successive ties if the crib widths differ substantially. Each tamping tool assembly may be independently lowered and operated but the construction is such that the vertical adjustment of the tamping tool assemblies may be obstructed. Tamping machines of the type disclosed in this patent have not been commercially successfully used in the simultaneous tamping of two successive ties, much less for successively tamping single ties.
U.S. Pat. No. 4,466,355 discloses a tamping unit comprising a vertically adjustable tamping tool carrier frame supporting two transversely adjacent tamping picks forming a twin tamping tool for immeriion at one side of the rail adjacent a respective tie, one of the tamping picks of the twin tamping tool being vertically retractible by an additional vertical adjustment drive. This so-called half tamping unit enables only one side of the rail/tie intersection to be tamped. Tamping units of this type are useful only for small tampers designed for tamping single ties at one side of the rail, and when they are alternately used at the right and left side of the rail, they cause considerable ballast dislocations, making proper tamping and the provision of a solid ballast bearing for the rail/tie intersection impossible.
My effectively copending U.S. Pat. No. 4,537,135, dated Aug. 27, 1985, for the first time disclosed a commercially successful tamping head universally useful for production and switch tamping, the tamping head comprising eight independently laterally pivotal tamping tools which may be selectively operated for tamping in switch areas or for production tamping. However, this tamping head can be used only for tamping one tie at a time.
Finally, one embodiment disclosed in my copending U.S. Pat. No. 4,643,101 dated Feb. 17, 1987 comprises a high-efficiency mobile track leveling, lining and tamping machine which advances continuously along a track while its tamping head advances intermittently from tamping station to tamping station and is designed for simultaneous tamping of two successive ties. Such machines are very useful in rehabilitation operations on high-speed tracks. A properly centered and trouble-free immersion of the tamping tools in the ballast is of particular importance in the operation of these machines which work at high speeds and require avoidance of obstacles and difficulties of any kind in the disposition of the tamping tools in the cribs.